Novel cancer treatments could be realized by marrying radioimmunotherapy (RAIT) with nanotechnology. In this application for a Mentored Quantitative Research Career Development Award (K25), the Candidate proposes to increase the efficacy of RAIT in the setting of malignant solid tumors by packaging radioisotopes in the form of nanoparticles (NPs). This project is a unique collaboration between Candidate Dr. Brian Smith and Mentor Dr. Gregory Adams, who is a respected expert in radioimmunotherapy. The central hypothesis is that immunologically targeted radioactive nanoparticles will prove more therapeutically effective against solid tumors than is typical for RAIT conjugates. This hypothesis will be tested using rhenium radiometal, which has two useful isotopes for RAIT, and single chain Fv (scFv) antibodies which target the tumor-associated HER2/neu antigen. Three sets of experiments are proposed. The first set (Aim 1) focuses on the synthesis of water soluble rhenium NPs. The second set (Aim 2) relates to attachment of scFv molecules to the NPs, and to quantification of the in vitro performance of these nanoparticle radioimmunoconjugates (NPRICs). The results will guide changes to the synthesis parameters in order to produce NPRICs with promising properties for in vivo application. In the third set (Aim 3), the biodistribution and treatment efficacy of optimized NPRICs will be studied in immunodeficient mice with tumor xenografts. Execution of this project will provide Dr. Smith, who is trained as a materials scientist, with the necessary knowledge and skills to pursue a cross-disciplinary career in the application of nanotechnology to cancer detection and treatment. Specific career goals are (a) education in the areas of nuclear medicine, immunology, and cancer physiology, (b) training in biomedical laboratory practices including immunochemistry and radiochemistry, and (c) training in the proper conduct of animal studies.